U.S. patent number 7,033,451 [Application Number 10/820,234] was granted by the patent office on 2006-04-25 for method and apparatus for ultrasonically stomping slider end stops on zipper.
This patent grant is currently assigned to Illinois Tool Works Inc.. Invention is credited to Donald L. Crevier, Nigel D. Knight, Michael J. McMahon, Stanley Piotrowski, Michael A. Pollack, Lawrence Share.
United States Patent |
7,033,451 |
McMahon , et al. |
April 25, 2006 |
Method and apparatus for ultrasonically stomping slider end stops
on zipper
Abstract
An ultrasonic welding assembly comprising a horn, an anvil and
an anvil cover. The horn comprises a generally T-shaped flattening
surface and a rail projecting forward of the flattening surface.
The rail is shaped to serve as a dam for flowing thermoplastic
zipper material during stomping of slider end stops. The horn
further comprises a plurality of vertical energy directors designed
to direct ultrasonic energy into the mass of zipper material and
deflect flowing zipper material toward the dam. The horn further
comprises first and second recesses located on opposite sides of a
stem of the T-shaped flattening surface. The anvil cover overlies
opposing portions of the anvil and comprises a T-shaped cutout. The
T-shaped flattening surface of the horn fits in the T-shaped cutout
of the anvil cover. The resulting zipper has slider end stops
located at opposing ends. Each end stop comprises flattened zipper
material having a plurality of spaced indentations, the
indentations being formed by the energy directors during stomping.
The zipper can be pre-heated prior to ultrasonic stomping. A flange
of the zipper can be cooled by fluid during ultrasonic stomping of
the zipper parts.
Inventors: |
McMahon; Michael J. (Palatine,
IL), Share; Lawrence (Skokie, IL), Pollack; Michael
A. (Vernon Hills, IL), Crevier; Donald L. (Essex,
IL), Knight; Nigel D. (Kankakee, IL), Piotrowski;
Stanley (Addison, IL) |
Assignee: |
Illinois Tool Works Inc.
(Glenview, IL)
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Family
ID: |
28041030 |
Appl.
No.: |
10/820,234 |
Filed: |
April 6, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040188000 A1 |
Sep 30, 2004 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10113489 |
May 11, 2004 |
6733622 |
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Current U.S.
Class: |
156/73.1;
156/290; 156/308.4; 156/580.2 |
Current CPC
Class: |
B29C
66/73921 (20130101); B29C 66/8322 (20130101); B29C
66/81429 (20130101); B29C 66/81419 (20130101); B29C
66/43121 (20130101); B29C 65/08 (20130101); B29C
66/326 (20130101); B29C 66/346 (20130101); B29C
66/43 (20130101); B65D 33/2591 (20130101); B29C
66/1224 (20130101); B29C 66/1222 (20130101); B29C
66/474 (20130101); B29C 66/81425 (20130101); B29C
66/81431 (20130101); B29C 66/81433 (20130101); B29C
66/71 (20130101); Y10T 156/1737 (20150115); B29C
66/0242 (20130101); B29C 65/18 (20130101); B29C
65/72 (20130101); B29C 66/1122 (20130101); B29C
66/349 (20130101); B29C 2793/009 (20130101); B29K
2023/0633 (20130101); B29K 2023/12 (20130101); B29K
2027/08 (20130101); B29K 2995/0025 (20130101); B29K
2995/0026 (20130101); B29L 2005/00 (20130101); B29L
2031/7129 (20130101); B29C 65/305 (20130101); B31B
70/8131 (20170801); B29C 66/71 (20130101); B29K
2077/00 (20130101); B29C 66/71 (20130101); B29K
2069/00 (20130101); B29C 66/71 (20130101); B29K
2067/006 (20130101); B29C 66/71 (20130101); B29K
2061/00 (20130101); B29C 66/71 (20130101); B29K
2059/00 (20130101); B29C 66/71 (20130101); B29K
2055/02 (20130101); B29C 66/71 (20130101); B29K
2027/06 (20130101); B29C 66/71 (20130101); B29K
2025/06 (20130101); B29C 66/71 (20130101); B29K
2023/12 (20130101); B29C 66/71 (20130101); B29K
2023/065 (20130101); B29C 66/71 (20130101); B29K
2023/0633 (20130101); B29C 66/71 (20130101); B29K
2023/0625 (20130101) |
Current International
Class: |
B29C
65/08 (20060101) |
Field of
Search: |
;156/73.1,290,308.2,308.4,553,580.1,580.2 ;264/442,443,445
;425/174.2 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sells; James
Attorney, Agent or Firm: Ostrager Chong Flaherty &
Broitman P.C.
Parent Case Text
RELATED PATENT APPLICATION
This application is a divisional of U.S. patent application Ser.
No. 10/113,489 filed on Apr. 1, 2002, which issued as U.S. Pat. No.
6,733,622 on May 11, 2004.
Claims
What is claimed is:
1. A method of manufacture comprising the following steps: (a)
forming first and second interlockable zipper parts having
respective base portions connecting a respective zipper flange to a
respective zipper profile, the respective base portions having
outermost portions disposed on opposite sides of the zipper when
the first and second zipper parts are interlocked; (b) interlocking
said first and second zipper parts; (c) inserting a slider on an
undeformed portion of said interlocked zipper parts; and (d)
transmitting sufficient ultrasonic wave energy into a T-shaped area
of said interlocked zipper parts to cause said interlocked zipper
parts to flatten and fuse in said T-shaped area, the outermost
portions of the base portions of said interlocked zipper parts
being undeformed on both sides of a stem of said T-shape.
2. The method as recited in claim 1, further comprising the step of
directing said ultrasonic wave energy to form a series of spaced
indentations in said flattened T-shaped area.
3. The method as recited in claim 1, further comprising the step of
pre-heating at least one of said zipper parts prior to said step of
transmitting ultrasonic wave energy.
4. The method as recited in claim 1, further comprising the step of
directing cooling fluid toward a flange of at least one of said
zipper parts during said step of transmitting ultrasonic wave
energy.
5. The method as recited in claim 1, wherein said stem of said T
shape is oriented generally transverse to a machine direction,
further comprising the steps of: (e) joining respective flanges of
said first and second zipper parts to first and second portions of
film material along respective first and second band-shaped zones
disposed generally parallel to said machine direction; (f) placing
said first and second portions of film material in opposing
relationship; and (g) cross sealing the first and second portions
in opposing relationship along a strip-shaped area generally
oriented in the transverse direction, wherein the strip-shaped area
of cross sealing overlaps the flattened T-shaped area.
6. The method as recited in claim 5, wherein step (f) is performed
prior to step (e).
7. The method as recited in claim 5, further comprising the step of
cutting the cross-sealed strip of the opposing portions of web
material along a line generally oriented in the transverse
direction, the cut generally bisecting the flattened T-shaped
area.
8. A method of manufacture, comprising the following steps: joining
interlocked zipper parts to respective band-shaped portions of
first and second webs of film material; ultrasonically deforming
the zipper parts to form a flattened T-shaped area having a stem
oriented generally transverse to a machine direction; cross sealing
opposing portions of said first and second webs of film material
along a strip-shaped area generally oriented in the transverse
direction, the strip-shaped area of cross sealing overlapping the
flattened T-shaped area; and cutting the cross-sealed strip of the
opposing portions of said first and second webs along a line
generally oriented in the transverse direction, the cut generally
bisecting the flattened T-shaped area.
9. The method as recited in claim 8, wherein said deforming step
comprises the steps of flattening the zipper material at the ends
of the zipper parts and forming a series of spaced indentations in
the flattened T-shaped area.
10. The method as recited in claim 8, further comprising the step
of pre-heating at least one of the zipper parts prior to
ultrasonically deforming the zipper parts.
11. The method as recited in claim 8, further comprising the step
of directing cooling fluid toward a flange of at least one of the
zipper parts during the ultrasonic deformation.
12. The method as recited in claim 8, wherein said first and second
webs are connected by a fold line.
13. A method of manufacture, comprising the following steps: (a)
forming first and second interlockable zipper parts, said first
zipper part comprising a first base, a first profiled closure
element projecting from one side of said first base, and a first
flange having a proximal end connected to said first base, and said
second zipper part comprising a second base, a second profiled
closure element projecting from one side of said second base, and a
second flange having a proximal end connected to said second base,
wherein respective first portions of said first and second bases
adjacent the connection with said first and second flanges
respectively have an outer dimension greater than an outer
dimension of respective second portions of said first and second
bases remote from the connection with said first and second flanges
respectively when said first and second zipper parts are
interlocked; (b) interlocking said first and second zipper parts;
(c) inserting a slider on an undeformed portion of said interlocked
first and second zipper parts, said slider comprising respective
hooks that latch under said first portions of said first and second
bases of said zipper to retain said slider on said zipper; and (d)
ultrasonically deforming said first and second zipper parts to form
a flattened area, said flattened area comprising a central region
wherein said first and second zipper parts are flattened over the
full height of said first and second bases, and first and second
regions on opposite sides of and contiguous with said central
region wherein said first and second zipper parts are flattened
over partial heights of said first and second bases, said first
portions of said first and second bases being not flattened in said
first and second regions.
14. The method as recited in claim 13, further comprising the
following steps: (e) joining said first and second flanges to
respective band-shaped zones on first and second portions of film
material; (f) cross sealing opposing regions of said first and
second portions of said film material along a strip-shaped area
generally oriented in the transverse direction, the strip-shaped
area of cross sealing overlapping the flattened T-shaped area; and
(g) cutting the cross-sealed strip of said first and second
portions of said film material along a line generally oriented in
the transverse direction, the cut generally bisecting the flattened
T-shaped area.
15. The method as recited in claim 14, wherein said first and
second portions of said film material are connected by a fold
line.
16. The method as recited in claim 13, wherein said first and
second zipper parts are formed by extrusion.
17. The method as recited in claim 13, wherein said deforming step
comprises the step of forming a series of spaced indentations in
the flattened T-shaped area.
Description
BACKGROUND OF THE INVENTION
This invention generally relates to slider-operated flexible
zippers for use in reclosable pouches, bags or other packages of
the type in which perishable material, such as foodstuff, may be
stored.
Reclosable fastener assemblies are useful for sealing thermoplastic
pouches or bags. Such fastener assemblies often include a plastic
zipper and a slider. Typically, the plastic zippers include a pair
of interlockable fastener elements, or profiles, that form a
closure. As the slider moves across the profiles, the profiles are
opened or closed. The profiles in plastic zippers can take on
various configurations, e.g. interlocking rib and groove elements
having so-called male and female profiles, interlocking alternating
hook-shaped closure elements, etc.
Conventional slider-operated zipper assemblies typically comprise a
plastic zipper having two interlocking profiles and a slider for
opening and closing the zipper. In one type of slider-operated
zipper assembly, the slider straddles the zipper and has a
separating finger at one end that is inserted between the profiles
to force them apart as the slider is moved along the zipper in an
opening direction. The other end of the slider is sufficiently
narrow to force the profiles into engagement and close the zipper
when the slider is moved along the zipper in a closing
direction.
Other types of slider-operated zipper assemblies avoid the use of a
separating finger. For example, U.S. Pat. No. 5,809,621 discloses a
slider-operated zipper assembly wherein one zipper profile has a
pair of handles that cooperate with the slider. As the slider is
moved in an opening direction, the handles are squeezed together to
disengage the profiles. In U.S. Pat. No. 5,442,838, a
slider-operated zipper assembly is disclosed wherein the zipper
profiles are engaged and disengaged in the course of a so-called
"rolling action". This "rolling action" is described as being
achieved through cooperation between flanges on the profiles and
shoulders that project inwardly from the arms of the slider. U.S.
Pat. No. 6,047,450 discloses a zipper comprising a pair of mutually
interlockable profiled structures. The first profiled structure
comprises an interlocking element on a surface directed toward the
second profiled structure and an integral base directed away from
the second profiled structure. Likewise, the second profiled
structure comprises an interlocking element on a surface directed
toward the first profiled structure and an integral base directed
away from the first profiled structure. Additionally, portions of
the two profiled structures form a fulcrum about which the profiled
structures may be pivoted out of engagement when lower edges of the
bases are forced towards each other.
One of the important features of such reclosable fastener
assemblies are the end stops, which prevent the slider from falling
off the end of the fastener when the slider reaches the end of the
fastener. End stops have taken on various configurations, such as,
for example, riveted end clamps such as those described in U.S.
Pat. Nos. 5,067,208 and 5,161,286; transverse end stops made from
molten material of the fastener strips, as described in U.S. Pat.
No. 5,088,971; reciprocating anvils, as described in U.S. Pat. No.
5,131,121; tubular end stops, as described in U.S. Pat. No.
5,405,478; a window structure combined with sealed zipper ends, as
described in U.S. Pat. No. 5,442,837; or plastic end clips fused to
the zipper as described in U.S. Pat. No. 5,448,807.
U.S. Pat. No. 5,950,285 discloses a reclosable bag having end stops
that prevent a slider from moving beyond the end of the zipper when
the slider reaches either the closed or fully open position. The
end stops are formed from the material of the zipper profiles and
"rise vertically" from the zipper to block and prevent further
movement of the slider. The end stops are formed by first aligning
together the opposing profiles at an end stop area proximate to an
end of the bag, and then fusing the zipper profiles at the end stop
area to provide a vertical structure for preventing movement of the
slider past the ends of the zipper, while at the same time keeping
the rails intact. Preferably, the profiles are fused by directing
ultrasonic energy to the end stop area. Optionally, the end stops
have ridges disposed along their surfaces.
In addition, U.S. Pat. No. 6,357,914 discloses a slider-operated
zipper in which the ends of the zipper profiles are deformed or
"crushed" to form slider end stops. Preferably, the slider end
stops are formed by the application of ultrasonically generated
heat and pressure to the ends of the zipper profiles. The sides of
the zipper profiles are softened and compressed at end stop areas
so as to impart a pre-selected width and an upwelling displacement
above the uppermost surfaces of the zipper profiles. The material
displaced above the upper surface of the zipper profiles interferes
with the top wall and ends of the slider to limit its sideways
travel along the zipper. The slider end stops (that is, the
deformed portions of the zipper profiles) are configured to avoid
deformation of the bottom surfaces of the zipper profiles. The
lower ends of the zipper profiles extend undeformed substantially
to the side edges of the package. The end stops and the undeformed
bottom surfaces of the zipper profiles in the area of end stops
cooperate to hold the slider, preventing the slider from being
unintentionally derailed. The '914 patent asserts that separation
of the "crushing" operation performed on the zipper profiles to
form the slider end stops from the conduction heat sealing
operation to form the side seals allows the end stops to be reduced
in size, effectively extending the size of the package opening
without sacrificing the ability of the end stops to effectively
retain the slider on the zipper.
There is a need for a method and an apparatus for ultrasonically
deforming the ends of a slider-operated zipper to form structures
capable of stopping a slider from sliding off an end of the zipper
when incorporated in reclosable packaging.
BRIEF DESCRIPTION OF THE INVENTION
The invention is directed to a method and an apparatus for
ultrasonically stomping the ends of a flexible zipper for forming
slider end stops in a reclosable package. The invention is further
directed to slider-operated zippers having stomped ends of a
particular structure and reclosable packages incorporating such
zippers.
One aspect of the invention is an ultrasonic welding assembly
comprising a horn and an anvil, wherein the horn comprises a
generally T-shaped flattening surface.
Another aspect of the invention is an ultrasonic welding assembly
comprising a horn and an anvil, wherein the horn comprises a
flattening surface and a plurality of projections projecting out of
the flattening surface. Each projection comprises first and second
surfaces that are neither parallel nor perpendicular to the
flattening surface. The first and second surfaces are inclined at
different angles.
Yet another aspect of the invention is an ultrasonic welding
assembly comprising a horn having a flattening surface of
predetermined shape, an anvil and an anvil cover overlying opposing
portions of said anvil, wherein the anvil cover comprises a cutout
and the flattening surface of the horn fits in the cutout.
A further aspect of the invention is an assembly comprising a
flexible zipper and a slider mounted to the zipper, wherein the
zipper comprises a first zipper part comprising a first
interlockable element and a second zipper part comprising a second
interlockable element, the first and second interlockable elements
being mutually interlockable, and the zipper further comprising
first and second slider end stops located at opposing ends of the
zipper parts, wherein each end stop comprises flattened zipper
material having a plurality of spaced spot-shaped indentations.
Yet another aspect of the invention is a package comprising a
receptacle, a flexible zipper joined to the receptacle and a slider
mounted to the zipper, wherein the zipper has the structure
described in the preceding paragraph.
Another aspect of the invention is a method for forming a slider
end stop on a flexible zipper. The method comprises the following
steps: interlocking first and second parts of a zipper; inserting a
slider on the interlocked zipper parts; and transmitting sufficient
ultrasonic wave energy into a T-shaped area of the interlocked
zipper parts to cause the latter to flatten and fuse in the
T-shaped area. The rails of the interlocked zipper parts are
undeformed on both sides of a stem of the T-shape.
Other aspects of the invention are disclosed and claimed below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic showing a reclosable package having a
slider-operated zipper with end stops in accordance with one
embodiment of the invention.
FIG. 2 is a schematic showing a typical ultrasonic welding
apparatus for welding thermoplastic material.
FIG. 3 is a schematic showing an end view of a zipper sandwiched
between a horn and an anvil at the start of ultrasonic stomping in
accordance with one embodiment of the invention.
FIGS. 4-6 are schematics respectively showing bottom, front and end
views of a horn in accordance with one embodiment of the
invention.
FIG. 7 is a schematic showing a top view of an anvil in accordance
with one embodiment of the invention.
FIG. 8 is a schematic showing an end view of the anvil depicted in
FIG. 7, with a dowel pin inserted in a hole formed in the
anvil.
FIGS. 9-11 are schematics showing cross-sectional views of the
anvil depicted in FIG. 7, with the sections being taken along the
lines respectively indicated by 9--9, 10--10 and 11--11 in FIG.
7.
FIG. 12 is a schematic showing a magnified view of the area
indicated by reference numeral 12 in FIG. 8.
FIGS. 13-15 are schematics showing bottom, front and end views of
an anvil cover in accordance with one embodiment of the
invention.
FIG. 16 is a schematic showing an end view of an anvil cover with
an air blast passageway in accordance with another embodiment of
the invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made to the drawings, in which similar
elements in different drawings bear the same reference numerals. A
reclosable package or bag 10 having a flexible plastic zipper 12
operated by manipulation of a slider 14 is shown in FIG. 1. It
should be understood that the slider-zipper assemblies disclosed
herein can be installed in a reclosable package or bag of the type
shown in FIG. 1 or other types of reclosable packages having
different structures.
Still referring to FIG. 1, the bag 10 may be made from any suitable
sheet material or plastic film and comprises opposing wall panels
(only the front panel 16 is visible in FIG. 1), which may be
secured together at opposite side edges of the bag by seams 18 and
20 (indicated by dashed lines). The opposing bottoms of the wall
panels may be joined, for example, by means of a heat seal made in
conventional fashion, e.g., by application of heat and pressure or
ultrasonic energy. Typically, however, the bottom of the package is
formed by a fold 16 in the original packaging film, as seen in FIG.
1.
At its top end, the bag 10 has an openable mouth, on the inside of
which is an extruded plastic zipper 12. The zipper 12 comprises a
pair of interlockable fastener strips or zipper halves 24 and 26
(best seen in FIG. 3). Although FIG. 3 shows a rib and groove
arrangement, the profiles of the zipper halves may take any form.
For example, the zipper may comprise interlocking rib and groove
elements or alternating hook-shaped closure elements. The preferred
zipper material is polyethylene.
The front and rear bag wall panels 16, 32 (seen in FIG. 3) are
respectively sealed to the zipper halves by heat fusion or welding.
Alternatively, the interlockable zipper halves can be attached to
the wall panels by adhesive or bonding strips or the zipper
profiles can be extruded integrally with the bag material. For the
purpose of joinder, the zipper halves-may be provided with
respective extension flanges 28, 30, to which an upper portion of
the respective bag wall panel is fused or welded. The walls of the
bag may be formed of various types of thermoplastic material, such
as low-density polyethylene, substantially linear copolymers of
ethylene and a C3-C8 alpha-olefin, polypropylene, polyvinylidene
chloride, mixtures of two or more of these polymers, or mixtures of
one of these polymers with another thermoplastic polymer. The
person skilled in the art will recognize that this list of suitable
materials is not exhaustive. The bag material may be either
transparent or opaque. The bottom edge of extension flange 28 is
indicated by a dashed line in FIG. 1 for the case where the bag
wall panels are opaque.
Optionally, the bag 10 may be provided with an enclosed header 38,
indicated by dashed lines in FIG. 1, which encompasses the zipper
and the slider. Alternatively, the header may be provided with
openings on both sides at the closed position of the slider, with
the openings being sized and shaped to allow the slider to protrude
through the openings on both sides of the header. The header 38 may
be a panel or strip formed from the same material as that
comprising the walls of the package or from the same material as
that comprising the zipper or from an entirely separate material.
More specifically, the header may comprise a panel of thermoplastic
material that is heat sealed or ultrasonically welded to either the
zipper flanges or the package walls. Alternatively, the header may
be formed as an extension of the zipper flanges or the package
walls.
In zippered bags with sliders, as the slider moves across the
zipper, the zipper is opened or closed. As shown in FIG. 1, the
slider is slidable along the zipper in a closing direction "C",
causing the zipper halves to become engaged, or in an opening
direction "O", causing the zipper halves to become disengaged.
The slider for opening or closing the reclosable zipper is
generally shaped so that the slider straddles the zipper profiles.
The slider may be made in multiple parts and welded together or the
parts may be constructed to be snapped together. The slider may
also be of one-piece construction. The slider can be made using any
desired method, such as injection molding. The slider can be molded
from any suitable plastic, such as nylon, polypropylene,
polystyrene, acetal, polyketone, polybutylene terephthalate,
high-density polyethylene, polycarbonate, or ABS.
The bag shown in FIG. 1 further comprises end stops 34 and 36 for
preventing the slider from sliding off the end of the zipper when
the slider reaches the closed or fully opened position. Such end
stops perform dual functions, serving as stops to prevent the
slider from going off the end of the zipper and also holding the
two zipper profiles together to prevent the bag from opening in
response to stresses applied to the profiles through normal use of
the bag. In accordance with one embodiment of the invention, the
end stops comprise stomped areas on the zipper profiles themselves.
The stomped end stops comprise sections of the profiles that have
been fused together and flattened proximate to the open and closed
slider positions. During deformation, thermoplastic zipper material
flows upward such that the end stops are raised in height above the
peak of the undeformed zipper on which the slider rides. Stomping
is carried out using ultrasonic welding equipment of the type
disclosed herein. As seen in FIG. 1, each end stop 34, 36 has a
plurality (i.e., two or more) of spaced indentations 64 that are
formed during ultrasonic welding for reasons to be described in
detail below.
Welding and sealing of thermoplastic material by ultrasonic
vibrations is an established process and has been used for forming
slider end stops on the ends of a slider-operated zipper in a
reclosable package. FIG. 2 shows a typical ultrasonic welding
apparatus in which a workpiece 40 is fed through an ultrasonic weld
station comprising an anvil 42 and an oppositely disposed resonant
horn 44. The frontal surface 46 of the horn 44 and the anvil 42 are
urged toward mutual engagement by force means, not shown, for
causing the horn to be in forced contact with the workpiece for
coupling the ultrasonic vibrations into the material, thereby
effecting ultrasonic welding. The horn 44 is energized from a power
supply 48 that provides electrical high-frequency power at a
predetermined ultrasonic frequency via a cable 50 to an
electroacoustic transducer 52, which, in turn, provides mechanical
vibrations at that frequency to a booster or coupling horn 54 for
coupling these vibrations to the horn 44. The horns 44 and 54 and
the transducer 52 are dimensioned to be mechanically resonant
longitudinally at the predetermined frequency. This combination of
components forming an ultrasonic welding apparatus is well known to
those skilled in the art.
The present invention is directed in part to an apparatus for
ultrasonic welding. Its application in a method for ultrasonically
stomping slider end stops on a flexible zipper of a reclosable
package will be disclosed herein. However, the apparatus disclosed
herein is not limited in its application to a particular type of
workpiece.
The horn and anvil of the ultrasonic welding-apparatus disclosed
herein are specifically designed so that the ultrasonic stomping
operation accomplishes at least some of the following goals: create
a vertical hump on the zipper to stop the slider; preserve the base
of the zipper profile to resist pull-off of the slider; penetrate
the heat into the mass of the zipper profile in the end stop areas
and melt the hooks of the zipper profiles to each other and into
the base; prevent the zipper from opening or shifting during
stomping; direct the flow of the molten plastic upward toward the
hump-stop at the ends of the stomp; control the heat of the plastic
to prevent hot spots that cause holes in the bag and prevent the
flange attachment from burning, away from the base of the zipper;
and guiding/locating the zipper in the stomper. Various designs in
horns and anvils were tried with matched contours, base guide
grooves, holding and energy-directing teeth, a "dam" to control the
material flow, heated anvil, etc., all to help shape the end stomp.
Special guides and cover plate designs were developed to guide the
profile at the ultrasonic stomp and to direct cooling toward the
ends of the stomp. The horn and anvil were designed to provide end
stomps with improved appearance and high end pull-off forces.
Referring to FIG. 3, the ultrasonic welding apparatus comprises a
horn 56 and an anvil 58, which are brought together with the
flexible zipper of a reclosable package therebetween. As will be
explained in more detail below, the anvil 58 comprises a slot 60 in
which a portion of one zipper half, e.g., zipper half 24 having a
male profile, is inserted, while the horn comprises a plurality of
teeth 62, which penetrate into the mass of thermoplastic material
forming the zipper half 26 having a female profile. Although
placing the zipper half with the female next to the horn is
preferred, this is not mandatory. During the ultrasonic stomping
procedure, the horn 56 is displaced downward and toward the
stationary anvil 58. FIG. 3 shows the horn 56 in a position whereat
the teeth 62 have just come into contact with the zipper half 26.
The horn is activated to couple ultrasonic waves into the zipper
material while applying pressure. As a result, portions of the
zipper halves 24 and 26 will be deformed and flattened, with
indentations (64 in FIG. 1) being formed in the flattened
thermoplastic material by the teeth 62. The portion of the zipper
halves that is flattened is determined by the extent of the
flattening surface 65 of the horn 56. As seen in FIG. 3, the horn
has a recess 66 where no flattening occurs, i.e., the base portions
or rails of the zipper halves 24 and 26 are left undisturbed.
Preferably, the boundary 72 of the recess 66 is generally aligned
with the left-hand (as seen in FIG. 3) wall of the slot 60 in the
anvil 58. The horn 56 further comprises a beveled surface 74 having
a juncture with wall 72 and a juncture with the flattening surface
65.
An additional structural feature seen in FIG. 3 is a rail 68 that
projects downward of the flattening surface 65. As will be
explained in more detail below, the rail 68 serves as a dam for
blocking and deflecting the flow of thermoplastic material across
the flattening surface during the ultrasonic stomping operation.
The confronting wall 68 of the dam is represented by a dashed line
in FIG. 3 because it is hidden behind a side rail 70 from the
vantage shown in FIG. 3.
The horn in accordance with one embodiment of the invention will
now be described in more detail with reference to FIGS. 4-6. This
horn design has a rectangular shape with a minimum size footprint
in order to maximize the focus of the ultrasonic wave energy at
high bag line speeds and to avoid leaker bags by directing the
vibrational energy into the mass of the zipper and away from the
flange attachment location. As seen in FIG. 4, the face of the horn
that confronts the anvil has a generally T-shaped planar flattening
surface 65 with a wide stem 76 and a pair of arms 78 and 78'. When
the horn is installed in the ultrasonic welding apparatus, the
flattening surface 65 is substantially perpendicular to the
direction of horn displacement and generally parallel to the
opposing face of the anvil, as previously shown in FIG. 3. The stem
76 is flanked on both sides by respective recesses 66 and 66'. The
horn 56 comprises a pair of beveled surfaces 74 and 74'. Bevel 74
has a juncture with wall 72 of recess 66 and a juncture with the
flattening surface 65; similarly bevel 74' has a juncture with wall
72' of recess 66' and a juncture with the flattening surface 65.
The bevel 74 and 74' save more rail on the female zipper
profile.
The geometry of the flattened area causes the zipper material to be
heated by the ultrasonic energy while the recessed areas minimize
the clamping and prevents the material from heating. This causes
the zipper material to flow upward in a desired pattern above the
top of the zipper to assist in acting as a stop for the slider. The
geometry also causes flattening and localized clamping to cause
part of the bottom of the zipper at the base to stomp or crush
together at the center of the stomp while the recessed area of the
tooling prevents the thickness of the base from being reduced. The
preservation of this existing material thickness at the base of the
zipper profile, particularly at the outer edges of the length of
the stomp, is required for keeping the slider from rotating upward
and off the zipper at the park position.
The rectangular horn 56 has a rail 68 along the top at a special
depth and location to trap the top of the zipper material as it
melts and flows outward during stomping and acts as a dam when the
female profile is up against the horn. If the female profile is
down, the dam could be on the anvil. The sides of the dam, i.e.,
side rails 70 and 70', assist in abruptly shaping the melted
thermoplastic zipper material and packing it up into this area. In
the final product, this abrupt shape acts as an improved stop for
the slider to bump against, which increases the pull-off force. The
recessed areas act as transition zones that gradually decrease the
amount of compression at this location during the ultrasonic
stomping. This keeps the profile from becoming molten immediately
outside the edge of the dam, reduces stringing of the plastic, and
improves the appearance of the stomp. Optionally, a projection 80
(indicated by dashed lines in FIG. 4) in the shape of a so-called
"widow's peak" can be incorporated in the dam to redirect
thermoplastic material from the middle of the anvil and toward the
starting point of the end stop, thereby improving pull-off
resistance. For example, the profile of the widow's peak may be an
inverted trapezoid with side walls inclined at 45 degree
angles.
As best seen in FIG. 4, the horn 56 is provided with a multiplicity
of teeth arranged in a line at spaced intervals. In this
embodiment, two types of teeth are shown. A first plurality of
teeth 62b occupies a central section of the line of teeth, while a
second plurality of teeth 62a occupies flanking sections of the
line on opposite sides of the central section.
Each tooth 62a has a prismatic shape with an inclined surface and
three side wall surfaces, each of the three side walls being
perpendicular to the flattening surface 65, while the inclined
surface is inclined at an angle of 30 degrees relative to the
flattening surface. The profile of each tooth 62a is a right
triangle, as seen in FIG. 6. Thus, each tooth 62a has one
rectangular side wall and two triangular side walls, the triangular
side walls being mutually parallel and perpendicular to the
rectangular side wall. Likewise the inclined surface, which faces
the dam, is rectangular, as seen in FIG. 4. In the embodiment shown
in FIGS. 4-6, there are two teeth 62a projecting in part from arm
78 of the flattening surface 65 and in part from bevel 74; and two
teeth 62a projecting in part from arm 78' of the flattening surface
65 and in part from bevel 74'. The beveled surface is inclined at
an angle of 30 degrees (see FIG. 6) relative to the flattening
surface 65.
Each tooth 62b has the same width (i.e., distance between parallel
side walls) as the width of teeth 62a, but a different length (as
seen in FIG. 4) and a different geometry, as seen in FIG. 6 (where
a tooth 62b is shown behind a tooth 62a as seen from the side). In
the embodiment shown in FIGS. 3-6, each tooth has the shape of a
truncated prism. More specifically, each tooth 62b has two inclined
surfaces separated by an end facet (these three surfaces can be
seen in FIG. 4) and two mutually parallel side wall surfaces, each
of the two side walls being perpendicular to the flattening surface
65, while one inclined surface is inclined at an angle of 30
degrees relative to the flattening surface and the other inclined
surface is inclined at an, angle of 60 degrees relative to the
flattening surface. The former inclined surface faces toward the
dam, while the latter inclined surface faces away from the dam. The
profile of each tooth 62b is a trapezoid, as seen in FIG. 6. Thus,
each tooth 62b has two trapezoidal side walls that are mutually
parallel and perpendicular to the flattening surface 65. The end
facet of each tooth 62b is preferably parallel to the flattening
surface. In the embodiment shown in FIGS. 4-6, there are five teeth
62b projecting from stem 76 of the flattening surface 65.
The teeth 62b act as vertical energy directors to penetrate the
heat into the center of the zipper directly into the fulcrum area
of the profiles. The greatest amount of welded zipper material will
be produced in the locations penetrated by teeth 62b, so the teeth
need to be properly positioned vis-a-vis the zipper. Also, due to
the high cycle rate of the stomping requirement, it is important to
get the heat into the center of the zipper material mass as soon as
possible. The different angles of inclination of the inclined
surfaces enables each tooth 62b to act as a material flow director
to maximize the flow of the molten zipper material toward the dam
and minimize the flow toward the zipper flange. Also the peaked
teeth 62a help keep the zipper aligned during the stomping
operation as the teeth 62b heat and penetrate the outside of the
profile. The teeth keep the zipper from rocking open and
disengaging during the stomping. Alternating teeth can be
positioned on both the horn and anvil, but tests showed that teeth
on the horn are preferred because the zipper was more stable and
kept better alignment as the horn and anvil came together.
The edges 72 and 72' of the horn penetrate the zipper during
stomping at a position above the zipper base, which preserves the
lower part of the base and maintains the cross section width at the
edge of the bases. This provides for keeping the engagement of the
slider hooks around the base, which is important to keep the slider
from being pulled off the end stop.
The large stem 76 of flattening surface 65 of the horn serves to
flatten the bases of the zipper and weld the profiles together at
the center of the stomp. The T-shaped flattening surface allows for
crushing of the bases for a specified width only at the center in
order to prevent open end channel leakers, while maintaining the
integrity of the bases at the end of the stomp. The T-shaped horn
(or T-shaped anvil, if desired) reduces the thickness of the zipper
to an acceptable thickness at the cross seal and cut-off location
of the bag such that additional stomping will be minimal or not
required, especially on vertical consumer packaged goods
applications where space is limited.
The anvil in accordance with one embodiment of the invention will
be described with reference to FIGS. 7-12. As seen in FIG. 7, the
anvil 58 has a rectangular shape with a recess or slot (generally
indicated by arrow 82) of varying cross-sectional profile extending
in a longitudinal direction across the surface of the anvil. The
recess or slot 82 across the tooling preserves the base of the
zipper profiles across the entire length of the ultrasonic stomp.
This slot or recess also removes the clamping force along the
bottom of the length of the base where the flange attaches to the
zipper profile. The slot or recess 82 in the anvil (whether full or
partial in length) acts as a guide to prevent the zipper from
sliding or shifting out from under the horn during welding due to
the side forces caused by the angle of the wedge-shaped zipper seen
in FIG. 3. The slot in the anvil (whether full or partial in
length) also relieves the clamping force at the base of the wedge
shape and helps prevent the zipper from opening during crushing. If
the zipper rocks open during stomping, it can become misaligned and
the slider will not stay activated properly at the park position,
becoming deactivated. For this reason, the preferred way to stomp
the: profile is with the male profile down against the anvil.
Another way to prevent the wedge-shaped zipper from
rocking/pivoting open during the stomping procedure is to heat one
of the legs of the profile, either directly or through the anvil or
horn, in order to minimize its bend strength. For example, a
cartridge heater can be inserted in a recess formed in the anvil
underneath the surface opposing the horn to assist in pre-heating
the zipper in the stopped position and adding to the heating during
ultrasonic stomping.
In accordance with one embodiment of the invention, an anvil cover
is placed over the anvil. One embodiment of an anvil cover 96 is
depicted in FIGS. 13-15. The anvil cover has a T-shaped cutout 100
(best seen in FIG. 13) that is shaped to allow the T-shaped
flattening surface of the horn to pass through and close with the
anvil. The bottom surface of the anvil cover, which opposes the
anvil surface shown in FIG. 7, is shown in FIG. 13. As seen
therein, the anvil cover has a recess or slot 102 that overlies one
portion of the recess or slot (82 in FIG. 7) formed in the anvil
and a recess or slot 102' that overlies another portion of the
recess or slot in the anvil. The slots 102, 102' in the anvil
cover, in combination with slot 82 in the anvil, form a passageway
for the zipper to slide through. The cross-sectional profile of
slot 82 in the anvil 58 changes as seen in FIGS. 9-12. Slot
sections 84 (see FIG. 9) in the anvil have a rectangular profile;
slot sections 86 (see FIG. 10) in the anvil have a rectangular
profile with a slight bevel on one side; slot sections 88 (see FIG.
11) in the anvil have a rectangular profile with a larger bevel on
one side; and the slot end sections 90 (see FIG. 12) comprise three
converging surfaces. The angled slot end sections 90 at the outer
edges of the extended anvil and the angled slot end sections 106,
106' at the outer edges of slots 102, 102' of the anvil cover act
as built-in zipper guides that provide improved guidance and keep
the zipper from pivoting. The inner edges 104, 104' where the anvil
cover is cut-out act as guides to keep the base of the profile
aligned and to prevent the base from squeezing out toward the
flange when the stomping process starts. They also help the teeth
keep the zipper base in position during stomping.
The anvil and anvil cover are fastened together by spring-loaded
bolts (not shown). Proper alignment of the cover with the anvil is
ensured by a pair of dowel pins 94, only one of which is shown in
FIG. 8. Holes 92 (see FIG. 7) are provided in the anvil for
receiving one portion of the dowel pins, while holes 98 are
provided in the anvil cover for receiving another portion of the
dowel pins. The distance separating the centers of holes 92 in the
anvil equals the distance separating the centers of holes 98 in the
anvil cover. Alternatively, the anvil cover may incorporate a key
that matches a keyway formed in the anvil to guarantee the
alignment of components during stomping. The cover also contains a
seat 108 (see FIG. 15) configured to receive a heavy-duty spring
and bolt that hold the cover closed properly on the zipper.
Optionally, ergonomic levers (not shown) can be used to unload the
springs while threading the zippered film through the stomping
assembly.
Optionally, the anvil cover may incorporate a manifold and/or air
blast holes that provide cooling to the flange attachment location
of the zipper during ultrasonic heating/stomping. This will help
cool down the stomp after welding in order to avoid leaker bags and
also help set the shape of the stomp at high cycle rates.
Alternatively, the cut-out area 100 of the anvil cover can be used
to allow an air blast to reach the entire surface of the flange and
base area being crushed by the T-shaped flattening surface of the
horn.
Although the disclosed embodiment of the ultrasonic horn has a row
of spaced teeth, the teeth need not be arranged in a line. For
example, the teeth can be staggered. Nor must the teeth be shaped
to leave a square of rectangular indentation. The indentations
formed in the flattened zipper stomp area can be spots having other
geometries, e.g., circular or elliptical. Since ultrasonic energy
directors are needed most where the zipper material is thickest,
the teeth are placed so as to not form indentations near the peak
of the peak, where the zipper has minimal width.
FIG. 16 depicts another embodiment of an anvil cover 96' having a
recess 108 for receiving a spring, keyway 110 that fits in a
matching key on the anvil to align the tooling, an angled slot 112
for guiding and holding the zipper, and n air blast passageway 114.
The passageway 114 has first and second openings, wherein the first
opening is located on a side of the anvil cover adjacent the slot
112 and the second opening on the other side of the anvil is in
communication with a source of pressurized air (not shown).
In accordance with one method of manufacture, package film is paid
off a roll. Downstream a pull roller is provided for driving the
film through the machine. A folder plow positioned downstream of
the film roll folds the package film about a bottom crease (22 in
FIG. 1) to form opposing package walls. Zipper tape is paid off a
spool and fed between the advancing package walls. The zipper tape
is passed around a guide roller and fed in the machine direction at
a predetermined height from the bottom fold in the package film. At
a first sealing station, the zipper tape is sealed to the package
walls by a pair of horizontal sealing bars. After this sealing
operation, the packaging film is advanced one package increment.
The zipper tape is then stomped at a stomping station comprising
the horn and anvil disclosed herein, thereby forming slider end
stops. After stomping, the packaging film is again advanced one
package increment. Then at a second sealing station, the folded
film and zipper tape are cross-sealed by a pair of vertical sealing
bars to form discrete packages. Then at a cutting station, the
individual packages are cut from one another. The separated
packages are then ready to be filled. Alternatively, the packages
can be filled before cutting.
In accordance with one embodiment, the method for forming slider
end stops on the zipper comprises the following steps: joining
interlocked zipper parts to opposing walls of film material;
ultrasonically deforming the zipper parts to form a flattened
T-shaped area having a stem oriented generally transverse to the
machine direction; cross sealing the opposing webs of film along a
strip-shaped area generally oriented in the transverse direction;
and cutting the cross-sealed strip of the opposing webs along a
line generally oriented in the transverse direction, the cut
generally bisecting the flattened T-shaped area. Thus, during each
stomping operation, end stops at adjacent edges of successive
packages are formed. The strip-shaped area of cross sealing
overlaps the flattened T-shaped area. The deforming step comprises
the steps of flattening the zipper material at the ends of the
zipper parts and forming a series of spaced indentations in the
flattened T-shaped area. Optionally, the method further comprises
the step of pre-heating at least one of the zipper parts prior to
ultrasonically deforming the zipper parts. Optionally, the method
may further comprise the step of directing cooling fluid toward a
flange of at least one of the zipper parts during the ultrasonic
deformation.
In accordance with another embodiment, a module is attached to the
side of a form/fill/seal (FFS) machine. The module applies a slider
to the zipper and stomps the zipper, using a horn and anvil of the
type disclosed herein. These steps can be performed concurrently or
in alternating sequence. Then the prepared zipper/slider assembly
is fed into the FFS machine. Depending on the type of FFS machine,
the zipper/slider assembly is fed either longitudinal (in the
machine direction) or transverse (in the cross direction) to the
direction of film web advancement using a registered/guided method.
Then the flanges of the zipper halves are welded to the webs after
the slider insertion and zipper stomping procedures. The completed
web is then cross-sealed and cut-off in conventional fashion to
form a separate package.
While the invention has been described with reference to various
embodiments, it will be understood by those skilled in the art that
various changes may be made and equivalents may be substituted for
elements thereof without departing from the scope of the invention.
In addition, many modifications may be made to adapt a particular
situation to the teachings of the invention without departing from
the essential scope thereof. Therefore it is intended that the
invention not be limited to the particular embodiment disclosed as
the best mode contemplated for carrying out this invention, but
that the invention will include all embodiments falling within the
scope of the appended claims.
As used in the claims, the term "package" means a container, bag,
pouch or other receptacle for objects, material or stuff. A
container, bag, pouch or other receptacle is deemed to be a package
even if not yet packed with objects, material or stuff. As used in
the claims, the verb "joined" means fused, bonded, sealed, adhered,
etc., whether by application of heat and/or pressure, application
of ultrasonic energy, application of a layer of adhesive material
or bonding agent, interposition of an adhesive or bonding strip,
co-extrusion (e.g., of zipper and bag), etc.
* * * * *